Heavy-duty gears used in rail transit and wind power sectors often require carburizing treatment to enhance their wear resistance during service. However, conventional carburizing processes face certain limitations in improving efficiency. Studies have shown when the rare earth (RE) elements are involved in some way, the carburizing atmosphere may be modified, thus increase the carburizing efficiency, and further enhance the wear resistance of the steels. Nevertheless, most existing research has focused on introducing exogenous RE elements into the steel surface during the carburizing process, while the effect of RE addition during steelmaking on the wear resistance of carburized gear steel remains insufficiently explored. In this study, 18CrNiMo7-6 gear steels with different Ce addition were prepared and subjected successively to heat treating at 1150 ^oC for 6 h, forging at 900 ^oC to 1150 ^oC, normalizing treatment at 880 ^oC for 2 h and followed by carburizing, quenching and tempering etc. Then the effect of RE addition on their friction and wear behavior was characterized via oil-lubricated sliding wear tester, contact profilometry, white light interferometry, scanning electron microscopy, transmission electron microscopy, transmission Kikuchi diffraction, and X-ray photoelectron spectroscopy, in terms of the surface morphology, subsurface microstructure evolution, and oxide scale composition on wear tracks. The results indicate that Ce addition can effectively mitigate the abrasive wear and improve the friction and wear behavior of the carburized gear steels during the steady-state wear stage, transforming the wear mechanism from a coexistence of abrasive wear and oxidative wear to oxidative wear-dominated mechanism, thereby significantly enhancing the wear resistance of carburized gear steel. Compared with carburized gear steel without RE, the wear volume of the carburized gear steels with 0.0078%Ce and 0.0126%Ce (mass fraction) is reduced by 55.3% and 49.2%, respectively. The improved wear resistance after Ce addition may be attributed to the increased hardness of the carburized layer and the modification of inclusion in the steels. The low surface hardness of the steel without RE may facilitate severe abrasive wear and pronounced subsurface plastic deformation, which readily leads to oxide scale fragmentation. Ce addition may be conductive to increasing the surface hardness of carburized gear steels, alleviating the subsurface plastic deformation, facilitating the formation of compact oxide scale, and consequently enhancing the oxidative wear resistance. Nevertheless, with the increasing Ce content, the continuously increased surface hardness results in further suppression of subsurface deformation, and there exists an increase in inclusion population and size. These two factors lead to the formation of thin, discontinuously distributed oxide scales, thereby compromising the wear resistance.